The purpose of the symposium and the works collected in this book is to focus attention on the issues relating to antimicrobial susceptibility testing that face the clinical microbiologist in the last decade of the current century. The accent is placed on issues rather than actual methodology. The organizers felt that there was a wealth of information on the test systems available in the contemporary literature or as information that can be obtained from the instrument manufacturers. The only methods that have received specific attention are those that have been recently introduced or significantly modified in recent years. Of course the issues of the ’90’s are based on earlier developments, but because of many factors, the whole field appears to be more sharply defined in the ’90s than in the previous decade. Many of these factors are related to increased emphasis on cost containment or are related to valuable lessons learned from the proliferation of automated systems that occurred in the 1980s.